JP2017013564A - Pneumatic tire, and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of improving belt durability performance, and a method for manufacturing the same.SOLUTION: A pneumatic tire 1 includes: a groove lower profile part Pri where a profile Pr of an external crossing belt 142 has a shape projecting to a tire inner cavity side in a cross-sectional view in a tire meridian direction, and is positioned in a groove lower area Ai of an outermost peripheral direction major groove 22; a first profile part which has a shape projecting to the tire radial direction outside and is bonded to the tire width direction inner side end part of the groove lower profile part Pri; and a second profile part which has a shape projecting to the tire radial direction outside and is bonded to the tire width direction outer side end part of the groove lower profile part Pri.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a pneumatic tire and a manufacturing method thereof, and more particularly to a pneumatic tire capable of improving belt durability and a manufacturing method thereof.

  In a general pneumatic tire, there is a problem that a groove crack occurs at the groove bottom of the outermost circumferential main groove located on the outer side in the vehicle width direction when the tire is mounted on the vehicle. If this groove crack grows and reaches the belt layer, the belt durability performance of the tire is lowered, which is not preferable.

  In addition, although it has a solution subject different from this application, the technique described in patent documents 1-3 is known as a conventional pneumatic tire provided with the belt layer which has a characteristic cross-sectional shape.

JP 2002-187410 A JP 2012-131424 A JP 2013-47041 A

  An object of the present invention is to provide a pneumatic tire capable of improving belt durability and a method for manufacturing the same.

  In order to achieve the above object, a pneumatic tire according to the present invention includes a carcass layer, a pair of cross belts disposed on an outer periphery of the carcass layer, a tread rubber disposed on an outer periphery of the pair of cross belts, A pneumatic tire comprising a plurality of circumferential main grooves extending in the tire circumferential direction and a plurality of land portions defined by the circumferential main grooves, wherein the intersecting belt on the outer side in the tire radial direction is outside When the outer circumferential belt is defined as a cross belt, and the circumferential main groove at the outermost side in the tire width direction is defined as the outermost circumferential main groove, the profile of the outer cross belt in the tire meridian direction is A groove-shaped profile portion that is convex toward the cavity side and is located in a groove-lower region of the outermost circumferential main groove; a groove-shaped profile portion that is convex outward in the tire radial direction; A first profile portion connected to the tire width direction inner end portion of the tire portion, a second profile portion having a shape protruding outward in the tire radial direction and connected to the tire width direction outer end portion of the lower groove profile portion, It is characterized by providing.

  Further, the manufacturing method of the pneumatic tire according to the present invention is the manufacturing method of the pneumatic tire described above, in the green tire forming step, at the position corresponding to the outermost circumferential main groove of the outer cross belt. The method includes a step of forming a dent constituting the sub-groove profile portion, and a step of vulcanizing the green tire.

  In the pneumatic tire according to the present invention, the profile of the outer cross belt is provided with a lower groove profile portion that protrudes toward the tire lumen side in the lower groove region of the outermost circumferential main groove. Groove bottom gauge to outer cross belt increases. Thereby, the damage of the outer cross belt due to the growth of the groove crack is suppressed, and there is an advantage that the belt durability performance of the tire is improved.

FIG. 1 is a sectional view in the tire meridian direction showing a pneumatic tire according to an embodiment of the present invention. FIG. 2 is an enlarged view showing a tread portion of the pneumatic tire shown in FIG. 1. FIG. 3 is an enlarged view showing a sub-groove area Ai of the outermost circumferential main groove shown in FIG. FIG. 4 is an explanatory view showing the outer cross belt described in FIG. 2. FIG. 5 is an explanatory view showing a modified example of the pneumatic tire shown in FIG. 1. FIG. 6 is a chart showing the results of the performance test of the pneumatic tire according to the embodiment of the present invention.

  Hereinafter, the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. Further, the constituent elements of this embodiment include those that can be replaced while maintaining the identity of the invention and that are obvious for replacement. In addition, a plurality of modifications described in this embodiment can be arbitrarily combined within a range obvious to those skilled in the art.

[Pneumatic tire]
FIG. 1 is a sectional view in the tire meridian direction showing a pneumatic tire according to an embodiment of the present invention. This figure shows a cross-sectional view of one side region in the tire radial direction. The figure shows a radial tire for a passenger car as an example of a pneumatic tire.

  In the figure, the cross section in the tire meridian direction means a cross section when the tire is cut along a plane including a tire rotation axis (not shown). Reference sign CL denotes a tire equator plane, which is a plane that passes through the center point of the tire in the tire rotation axis direction and is perpendicular to the tire rotation axis. Further, the tire width direction means a direction parallel to the tire rotation axis, and the tire radial direction means a direction perpendicular to the tire rotation axis. Further, the inner side in the vehicle width direction and the outer side in the vehicle width direction are defined as directions with respect to the vehicle width direction when the tire is mounted on the vehicle. Here, of the left and right regions having the tire equator plane as a boundary, a region on the outer side in the vehicle width direction when the tire is mounted on the vehicle is called an outer region, and a region on the inner side in the vehicle width direction is called an inner region.

  The pneumatic tire 1 has an annular structure centered on the tire rotation axis, and includes a pair of bead cores 11, a pair of bead fillers 12, 12, a carcass layer 13, a belt layer 14, and a tread rubber 15. And a pair of sidewall rubbers 16 and 16 and a pair of rim cushion rubbers 17 and 17 (see FIG. 1).

  The pair of bead cores 11 and 11 is an annular member formed by bundling a plurality of bead wires, and constitutes the core of the left and right bead portions. The pair of bead fillers 12 and 12 are disposed on the outer circumference in the tire radial direction of the pair of bead cores 11 and 11 to constitute a bead portion.

  The carcass layer 13 has a single layer structure composed of a single carcass ply or a multilayer structure formed by laminating a plurality of carcass plies, and is bridged in a toroidal shape between the left and right bead cores 11 and 11 to form a tire skeleton. Configure. Further, both end portions of the carcass layer 13 are wound and locked outward in the tire width direction so as to wrap the bead core 11 and the bead filler 12. The carcass ply of the carcass layer 13 is formed by coating a plurality of carcass cords made of steel or an organic fiber material (for example, aramid, nylon, polyester, rayon, etc.) with a coat rubber and rolling it, and has an absolute value of 80 A carcass angle (defined as the inclination angle of the carcass cord in the longitudinal direction with respect to the tire circumferential direction) of [deg] or more and 95 [deg] or less.

  In the configuration of FIG. 1, the carcass layer 13 has a multilayer structure in which two carcass plies 131 and 132 are laminated. However, the present invention is not limited to this, and the carcass layer 13 may be configured by stacking three or more carcass plies, or may have a single-layer structure including one carcass ply (not shown). In the configuration of FIG. 1, the carcass layer 13 has a structure that is continuous in the tire width direction, and extends to the left and right regions of the tire crossing the tire equatorial plane CL. However, the present invention is not limited to this, and the carcass layer 13 may have a structure (a so-called carcass division structure) that includes a pair of left and right carcass plies and has a divided portion in the tread portion and is separated in the tire width direction (shown in the figure). (Omitted).

  The belt layer 14 is formed by laminating a pair of cross belts 141 and 142 and a pair of belt edge covers 143 and 143, and is arranged around the outer periphery of the carcass layer 13. The pair of cross belts 141 and 142 is formed by rolling a plurality of belt cords made of steel or organic fiber material with a coating rubber, and has an absolute value of a belt angle of 20 [deg] or more and 55 [deg] or less. Have. The pair of intersecting belts 141 and 142 have belt angles with different signs (defined as inclination angles in the longitudinal direction of the belt cord with respect to the tire circumferential direction), and intersect the longitudinal directions of the belt cords with each other. (So-called cross-ply structure). The pair of belt edge covers 143 and 143 are configured by coating a belt cord made of steel or an organic fiber material with a coat rubber, and have a belt angle of 0 [deg] or more and 10 [deg] or less in absolute value. The pair of belt edge covers 143 and 143 are, for example, a strip material formed by coating one or a plurality of belt cords with a coat rubber, and the strip material is disposed on the outer side in the tire radial direction of the cross belts 141 and 142 and on the tire. It is configured by winding a plurality of times in the circumferential direction and spirally. Further, the pair of belt edge covers 143 is disposed so as to cover only the left and right edge portions of the cross belts 141 and 142.

  Here, the cross belt 141 on the inner side in the tire radial direction is defined as the inner cross belt, and the cross belt 142 on the outer side in the tire radial direction is defined as the outer cross belt.

  The tread rubber 15 is disposed on the outer circumference in the tire radial direction of the carcass layer 13 and the belt layer 14 to constitute a tread portion of the tire. The tread rubber 15 includes a cap tread 151 and an under tread 152. The cap tread 151 is made of a rubber material having excellent grounding characteristics and weather resistance, and is exposed on the tread surface to constitute the outer surface of the tread portion. The under tread 152 is made of a rubber material having a lower altitude and superior heat resistance than the cap tread 151, and is disposed between the cap tread 151 and the belt layer 14 to constitute a base portion of the tread rubber 15. For example, in the configuration of FIG. 1, the cap tread 151 is disposed so as to cover the entire undertread 152 while sandwiching the undertread 152 between the belt layer 14 and the cap tread 151.

  The pair of side wall rubbers 16 and 16 are respectively arranged on the outer side in the tire width direction of the carcass layer 13 to constitute left and right side wall portions. For example, in the configuration of FIG. 1, the end portion of the sidewall rubber 16 on the outer side in the tire radial direction is disposed in the lower layer of the tread rubber 15 and is sandwiched between the belt layer 14 and the carcass layer 13. However, the present invention is not limited thereto, and the end portion of the sidewall rubber 16 on the outer side in the tire radial direction may be disposed on the outer layer of the tread rubber 15 and exposed to the buttress portion (not shown).

  The pair of rim cushion rubbers 17, 17 are respectively disposed on the inner side in the tire radial direction of the wound portions of the left and right bead cores 11, 11 and the carcass layer 13, and constitute the contact surfaces of the left and right bead portions with respect to the rim flange. For example, in the configuration of FIG. 1, the end portion of the rim cushion rubber 17 on the outer side in the tire radial direction is inserted into the lower layer of the sidewall rubber 16 and sandwiched between the sidewall rubber 16 and the carcass layer 13. ing.

  The inner liner 18 is an air permeation prevention layer that is disposed on the inner surface of the tire and covers the carcass layer 13, suppresses oxidation due to exposure of the carcass layer 13, and prevents leakage of air filled in the tire. The inner liner 18 is composed of, for example, a rubber composition mainly composed of butyl rubber, a thermoplastic resin, a thermoplastic elastomer composition obtained by blending an elastomer component in a thermoplastic resin, and the like.

  Further, the pneumatic tire 1 includes a plurality of circumferential main grooves 21 and 22 extending in the tire circumferential direction, a plurality of land portions 31 and 32 partitioned by the circumferential main grooves 21 and 22, and The tread portion includes a plurality of lug grooves (reference numerals omitted in the drawing) arranged in the land portions 31 and 32.

  The circumferential main groove is a circumferential groove having a wear indicator indicating the end of wear, and generally has a groove width of 5.0 [mm] or more and a groove depth of 7.5 [mm] or more.

  The groove width is measured as the maximum value of the distance between the left and right groove walls at the groove opening in a no-load state in which the tire is mounted on the prescribed rim and filled with the prescribed internal pressure. In the configuration where the land part has a notch part or a chamfered part at the edge part, the groove width is based on the intersection of the tread surface and the extension line of the groove wall in a cross-sectional view in which the groove length direction is a normal direction. Measured. In the configuration in which the groove extends in a zigzag shape or a wave shape in the tire circumferential direction, the groove width is measured with reference to the center line of the amplitude of the groove wall.

  The groove depth is measured as the maximum value of the distance from the tread surface to the groove bottom in an unloaded state in which the tire is mounted on the specified rim and filled with the specified internal pressure. Moreover, in the structure which a groove | channel has a partial uneven | corrugated | grooved part and a sipe in a groove bottom, groove depth is measured except these.

  The specified rim refers to an “applied rim” defined in JATMA, a “Design Rim” defined in TRA, or a “Measuring Rim” defined in ETRTO. The specified internal pressure means “maximum air pressure” defined by JATMA, the maximum value of “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined by TRA, or “INFLATION PRESSURES” defined by ETRTO. The specified load means the “maximum load capacity” defined by JATMA, the maximum value of “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined by TRA, or “LOAD CAPACITY” defined by ETRTO. However, in JATMA, in the case of tires for passenger cars, the specified internal pressure is air pressure 180 [kPa], and the specified load is 88 [%] of the maximum load capacity.

  For example, in the configuration of FIG. 1, the four circumferential main grooves 21 and 22 are arranged symmetrically about the tire equatorial plane CL. Further, five rows of land portions 31 to 33 are partitioned by the four circumferential main grooves 21 and 22. Further, one land portion 31 is disposed on the tire equator plane CL.

  However, the present invention is not limited to this, and three or more circumferential main grooves may be disposed, or the circumferential main grooves 21 and 22 may be disposed asymmetrically about the tire equatorial plane CL ( (Not shown). Further, the circumferential main groove 21 may be disposed on the tire equator plane CL, whereby the land portion 31 may be disposed at a position away from the tire equator plane CL (not shown).

  In addition, the circumferential main groove 22 on the outermost side in the tire width direction is defined as the outermost circumferential main groove. The outermost circumferential main grooves 22 are respectively defined in left and right regions with the tire equatorial plane CL as a boundary. Further, when one side region (including on the tire equator plane CL) having the tire equator plane CL as a boundary has two or more circumferential main grooves 21, 22, the tire equator plane adjacent to the outermost circumferential main groove 22 is used. The circumferential main groove 21 on the CL side is defined as the center circumferential main groove.

  Further, the land portion 33 on the outer side in the tire width direction defined by the outermost circumferential main groove 22 is defined as a shoulder land portion, and the land portion 32 on the inner side in the tire width direction is defined as a second land portion. Further, a land portion 31 on the tire equator plane CL or a land portion (not shown) partitioned in a circumferential main groove on the tire equator plane CL is defined as a center land portion. In the configuration in which one region having the tire equator plane CL as a boundary has a single circumferential main groove (not shown), the circumferential main groove becomes the outermost circumferential main groove and is partitioned into the outermost circumferential main groove. The land portion on the inner side in the tire width direction serves as the second land portion and the center land portion.

[Cross belt profile]
In a general pneumatic tire, there is a problem that a groove crack occurs at the groove bottom of the outermost circumferential main groove located on the outer side in the vehicle width direction when the tire is mounted on the vehicle. If this groove crack grows and reaches the belt layer, the belt durability performance of the tire is lowered, which is not preferable.

  Therefore, this pneumatic tire has the following configuration in order to suppress belt layer damage due to groove cracks and improve belt durability.

  FIG. 2 is an enlarged view showing a tread portion of the pneumatic tire shown in FIG. 1. This figure shows an enlarged view of the outer region in the vehicle width direction with the tire equatorial plane CL as a boundary. In the figure, the symbol T is a ground terminal. FIG. 3 is an enlarged view showing a sub-groove region Ai of the outermost circumferential main groove 22 shown in FIG. This figure shows the curved structure of the profiles of the cross belts 141 and 142 and the carcass layer 13 in the sub-groove region Ai. FIG. 4 is an explanatory view showing the outer cross belt 142 shown in FIG. This figure shows a cross-sectional view of the single outer cross belt 142 in the tire meridian direction.

  As shown in FIG. 2, the profile Pr of the outer cross belt 142 has a shape that is convex toward the tire lumen side and is located in the groove subregion Ai of the outermost circumferential main groove 22 in a cross-sectional view in the tire meridian direction. And a first profile portion having a shape protruding outward in the tire radial direction and connected to an inner end portion in the tire width direction of the lower groove profile portion Pri. (The portion having the radius of curvature Ro1 in FIG. 2; reference numerals omitted in the drawing) and a second profile that has a convex shape outward in the tire radial direction and that is connected to the outer end in the tire width direction of the lower groove profile portion Pri. (A portion having a radius of curvature Ro2 in FIG. 2; reference numerals omitted in the drawing). That is, the profile Pr of the outer cross belt 142 is convex toward the tire lumen side in the lower groove area Ai of the outermost circumferential main groove 22 and protrudes outward in the tire radial direction in the left and right areas of the lower groove area Ai. . Further, the profile Pr of the outer cross belt 142 has a uniform shape over the entire circumference of the tire.

  The profile is a contour line in a sectional view in the tire meridian direction, and is measured using a laser profiler in a no-load state in which the tire is mounted on a specified rim and filled with a specified internal pressure. As the laser profiler, for example, a tire profile measuring device (manufactured by Matsuo Corporation) is used. In particular, as shown in FIG. 4, the profile Pr of the outer cross belt 142 is defined as a curve that smoothly connects the outer circumferential surfaces of the belt cord 1421 of the outer cross belt 142 in the tire radial direction.

  Further, the sub-groove profile portion Pri, the first profile portion, and the second profile portion may be composed of a single arc or a plurality of smoothly connected arcs. When the under-groove profile portion Pri is composed of a plurality of arcs, the under-groove profile portion Pri is approximated by a single arc that protrudes toward the tire lumen, and a curvature radius Ri of the below-groove profile portion Pri described later is obtained. Measured. Similarly, when the first profile portion and the second profile portion are composed of a plurality of arcs, each profile portion is approximated by a single arc that protrudes outward in the tire radial direction, and a below-groove profile portion Pri described later. The curvature radii Ro1 and Ro2 are measured.

  The sub-groove region Ai is a region located on the tire lumen side of the outermost circumferential main groove 22 as described above, and as shown in FIG. 2, the outermost circumferential main groove in a sectional view in the tire meridian direction. It is defined as a region between one straight line that passes through the left and right open ends of 22 and is perpendicular to the profile of the tread surface. The left and right opening end portions of the outermost circumferential main groove 22 are defined as measurement points of the groove width GW of the outermost circumferential main groove 22 described later, as shown in FIG.

  The sub-groove profile portion Pri has a convex shape toward the tire lumen as described above, and is located in the sub-groove region Ai of the outermost circumferential main groove 22 (see FIG. 2). At this time, the entirety of the under-groove profile portion Pri may be included in the under-groove region Ai, or one or both ends of the under-groove profile portion Pri exceed the boundary of the under-groove region Ai and are outside in the tire width direction. You may project it. For example, in the configuration of FIG. 2, both end portions of the lower groove profile portion Pri and the left and right boundary lines of the lower groove region Ai are substantially at the same position.

  The curvature radius Ri of the sub-groove profile portion Pri is preferably in the range of 10 [mm] ≦ Ri ≦ 50 [mm], and more preferably in the range of 15 [mm] ≦ Ri ≦ 30 [mm]. preferable. In the configuration of FIG. 2, the sub-groove profile portion Pri is formed of a single arc that protrudes toward the tire lumen, and the center of the curvature radius Ri is on the groove center line of the outermost circumferential main groove 22. However, the present invention is not limited to this. For example, when the outermost circumferential main groove 22 has a left-right asymmetric cross-sectional shape, the center of the curvature radius Ri may be separated from the groove center line of the outermost circumferential main groove 22 (illustrated). (Omitted).

  As described above, the first profile portion has a curvature radius Ro1 that protrudes outward in the tire radial direction, and is positioned on the inner side in the tire width direction of the lower groove profile portion Pri (see FIG. 2). At this time, the first profile portion and the profile of the tread surface of the second land portion 32 wrap in the tire width direction. In the configuration of FIG. 2, the first profile portion extends beyond the tire equatorial plane CL from the inner end in the tire width direction of the lower groove profile portion Pri, so that both the center land portion 31 and the second land portion 32 are provided. It extends across. However, the present invention is not limited to this, and it is sufficient that the first profile portion extends over at least the region from the connection position with the below-groove profile portion Pri to the inner edge portion of the second land portion 32 in the tire width direction. Therefore, the profile Pr of the outer cross belt 142 may have a shape that protrudes toward the tire lumen in the region on the tire equator plane CL side with respect to the second land portion 32 (not shown).

  Moreover, it is preferable that the curvature radius Ro1 of a 1st profile part exists in the range of 150 [mm] <= Ro1 <= 2000 [mm], and it is more preferable to exist in the range of 400 [mm] <= Ro1 <= 1200 [mm]. . In the configuration of FIG. 2, the first profile portion is composed of a single arc that protrudes outward in the tire radial direction, and the center of the curvature radius Ro1 is on the tire equatorial plane CL. However, the present invention is not limited to this. For example, when the first profile portion is formed of a plurality of arcs that protrude outward in the tire radial direction, the radius of curvature Ro1 of the first profile portion is equal to the position of the center land portion 31 and the second land portion 32. The position may vary depending on the position (not shown).

  As described above, the second profile portion has a curvature radius Ro2 that is convex outward in the tire radial direction, and is positioned on the outer side in the tire width direction of the lower groove profile portion Pri (see FIG. 2). At this time, the profile of the second profile portion and the tread surface of the shoulder land portion 33 wrap in the tire width direction. In the configuration of FIG. 2, the second profile portion extends from the outer end portion in the tire width direction of the lower groove profile portion Pri to the outer edge portion in the tire width direction of the outer cross belt 142 beyond the ground contact end T. . However, the present invention is not limited to this, and it is sufficient that the second profile portion extends over at least the region from the connection position with the below-groove profile portion Pri to the grounding end T. Therefore, the profile Pr of the outer cross belt 142 may have a shape that protrudes toward the tire lumen portion in a region outside the tire ground contact end T in the tire width direction (not shown).

  The curvature radius Ro2 of the second profile portion is preferably in the range of 50 [mm] ≦ Ro2 ≦ 800 [mm], and more preferably in the range of 200 [mm] ≦ Ro2 ≦ 600 [mm]. . In the configuration of FIG. 2, the second profile portion is formed of a single arc that protrudes outward in the tire radial direction, and the center of the curvature radius Ro2 is on the tire equatorial plane CL. However, the present invention is not limited to this, and the curvature radius Ro2 of the second profile portion may change in the shoulder land portion 33 by the second profile portion being formed of a plurality of arcs that protrude outward in the tire radial direction (illustrated). (Omitted).

  Further, as described above, the first profile portion and the second profile portion are respectively connected to the left and right end portions of the lower groove profile portion Pri (see FIG. 2). At this time, as shown in FIG. 3, the lower groove profile portion Pri and the first profile portion and the second profile portion may be directly connected to each other, or have an arc shape, an S shape, or a linear shape. You may connect smoothly via a short connection part (illustration omitted).

  In addition, it is preferable that the connection portion between the sub-groove profile portion Pri and the first profile portion and the second profile portion satisfy the following condition. That is, as shown in FIG. 3, in a sectional view in the tire meridian direction, a virtual arc (broken line in FIG. 3) in contact with the first profile portion and the second profile portion, and the first profile portion on the virtual arc and The end points P1 and P2 on the lower profile portion Pri side of the second profile portion are defined. At this time, the distance Wb (Wb1 and Wb2 in FIG. 3) from the groove center line of the outermost circumferential main groove 22 to the end points P1 and P2 and the groove width GW of the outermost circumferential main groove 22 are 0.40 ≦ Wb. /GW≦0.80 is preferable, and 0.50 ≦ Wb / GW ≦ 0.65 is more preferable.

  Furthermore, it is preferable that the end point P2 on the outer side in the tire width direction is on the inner side in the tire width direction than the tire ground contact end T (see FIG. 2).

  The tire ground contact end T is a contact surface between the tire and the flat plate when a tire is mounted on a predetermined rim to apply a predetermined internal pressure and a load corresponding to the predetermined load is applied in a stationary state perpendicular to the flat plate. Is defined as the maximum width position in the tire axial direction.

  Moreover, it is preferable that the maximum protrusion amount D of the lower groove profile portion Pri with respect to the virtual arc is in a range of 0.6 [mm] ≦ D ≦ 3.3 [mm], and 1.4 [mm] More preferably, it is in the range of ≦ D ≦ 2.4 [mm].

  Further, the maximum protrusion amount D of the lower groove profile portion Pri with respect to the virtual arc and the lower groove gauge G1 of the outermost circumferential main groove 22 are 0.40 ≦ D / (G1-D) ≦ 1.70. It is preferable to have a relationship of 0.60 ≦ D / (G1-D) ≦ 1.50, and more preferable.

  Further, the relationship between the sub-gage gauge G1 ′ (not shown in the drawing) of the center circumferential main groove 21 and the sub-gage gauge G1 of the outermost circumferential main groove 22 is 0.6 [mm] ≦ G1-1 ′. And preferably has a relationship of 0.6 [mm] ≦ G1-1 ′. The upper limit of the difference G1-1 'is not particularly limited, but is limited by the relationship between the maximum protrusion amount D of the lower groove profile portion Pri and the lower groove gauge G1 of the outermost circumferential main groove 22.

  The maximum protrusion amount D is defined as the maximum value of the protrusion amount of the sub-groove profile portion Pri in the direction perpendicular to the tread profile.

  The sub-groove gauges G1 and G1 ′ (and G2 to be described later) are a belt cord (more specifically, an outermost layer) of the outermost layer of the belt layer below the groove of the circumferential main groove and the groove of the circumferential main groove. The distance between the belt cord and a circular arc connecting the apexes on the outer side in the tire radial direction is measured. In FIG. 3, since the outermost layer of the belt layer 14 below the outermost circumferential main groove 22 is the outer cross belt 142, the distance from the groove bottom of the outermost main groove 22 to the belt cord of the outer cross belt 142 is as follows. Measured as a sub-groove gauge G1. Further, for example, in a configuration in which the belt cover is disposed below the outermost circumferential main groove 22 (not shown), the distance from the groove bottom of the outermost circumferential main groove 22 to the belt cord of the belt cover is the lower groove gauge G1. As measured. That is, the sub-groove gauge G1 is defined as a gauge of the tread rubber 15 below the outermost circumferential main groove 22.

  In FIG. 4, in the passenger car tire, the outer diameter φ of the belt cord 1421 of the outer cross belt 142 is in the range of 0.23 [mm] ≦ φ ≦ 0.30 [mm]. Note that reference numeral 1422 in FIG. 4 is a coat rubber of the outer cross belt 142.

  The outer diameter of the belt cord is measured as the diameter of a circumscribed circle in a radial cross-sectional view of the cord in a configuration including a plurality of filaments in which the cord is twisted.

  In the above-described configuration, the groove Pr of the outermost circumferential main groove 22 is provided in the groove area Ai of the outermost circumferential main groove 22 with the lower groove profile portion Pri in which the profile Pr of the outer cross belt 142 is convex toward the tire lumen. A groove bottom gauge G1 from the bottom to the outer cross belt 142 is secured. Thereby, the damage of the outer cross belt 142 due to the growth of the groove crack is suppressed, and the belt durability performance of the tire is improved.

[Modification]
FIG. 5 is an explanatory view showing a modified example of the pneumatic tire shown in FIG. 1. This figure shows an enlarged view of the sub-groove region Ai of the outermost circumferential main groove 22.

  In the configuration of FIG. 1, as shown in FIG. 3, the outermost layer of the belt layer 14 is the outer cross belt 142, and the tread rubber 15 is disposed on the outer periphery of the outer cross belt 142. Further, in the sub-groove region Ai of the outermost circumferential main groove 22, the under tread 152 is positioned on the outer periphery of the outer cross belt 142, and the cap tread 151 is positioned on the outer periphery of the under tread 152. For this reason, the undertread 152 is filled in the recess of the lower groove profile portion Pri of the outer cross belt 142.

  In contrast, in the configuration of FIG. 5, the under-groove rubber 19 having different physical properties with respect to the tread rubber 15 is disposed in the recess of the under-groove profile portion Pri of the outer cross belt 142.

  Specifically, the under-groove rubber 19 has physical properties that are more excellent in heat resistance than the undertread 152. For example, in the configuration of FIG. 5, the tan δ value of the cap tread 151 is in the range of 0.03 to 0.030, and the tan δ value of the under tread 152 is in the range of 0.05 to 0.25. The tan δ value of the under-groove rubber 19 is preferably in the range of 105 [%] to 130 [%] with respect to the tan δ value of the undertread 152, and in the range of 110 [%] to 120 [%]. More preferably.

  Further, the sub-groove rubber 19 is disposed in a region surrounded by a virtual arc in contact with the first profile portion and the second profile portion and the outer peripheral surface of the outer cross belt 142. For example, in the configuration of FIG. 5, the under-groove rubber 19 is disposed between the under tread 152 and the outer peripheral surface of the outer cross belt 142 in the lower groove region Ai of the outermost circumferential main groove 22. . As a result, the under-groove rubber 19 is filled in the recess of the under-groove profile portion Pri of the outer cross belt 142.

  The tan δ value was measured using a viscoelastic spectrometer manufactured by Toyo Seiki Seisakusho under the conditions of temperature 60 [° C.], shear strain 10 [%], amplitude ± 0.5 [%], and frequency 20 [Hz]. Measured.

  In the above configuration, when the tire rolls, the grooved rubber 19 suppresses heat generation in the grooved area Ai of the outermost circumferential main groove 22, so that the growth of groove cracks due to the deterioration of the rubber in the grooved area Ai. Is suppressed. Thereby, the damage of the outer cross belt 142 due to the groove crack is suppressed.

  In the above-described configuration, it is preferable that the under-groove rubber 19 is disposed so as to fill 40% or more of the cross-sectional area of the enclosed region in a cross-sectional view in the tire meridian direction, and 60%. More preferably, the arrangement is filled up.

  In addition, the thickness G2 of the under-groove rubber 19 and the under-groove gauge G1 of the outermost circumferential main groove 22 may be in a range of 0.6 ≦ G2 / G1 ≦ 1.0 in a sectional view in the tire meridian direction. Preferably, the range is 0.7 ≦ G2 / G1 ≦ 0.9. G2 / G1 ≦ 1.0 is a state in which the under-groove rubber 19 extends from the outer peripheral surface of the outer cross belt 412 to the groove bottom of the outermost circumferential main groove 22 and is exposed to the groove bottom of the outermost circumferential main groove 22. means.

  In addition, the width Wg of the under-groove rubber 19 and the width GW of the outermost circumferential main groove 22 are preferably in the range of 0.7 ≦ Wg / GW ≦ 2.0 in a cross-sectional view in the tire meridian direction. More preferably, it is in the range of 1.0 ≦ Wg / GW ≦ 1.6.

  The thickness G2 and the width Wg of the under-groove rubber 19 are measured in a state where a tire is mounted on a specified rim to apply a specified internal pressure and no load is applied. The thickness G2 is measured as the maximum value of the thickness of the sub-groove rubber 19 in the direction perpendicular to the tread profile. The width Wg is measured as the maximum value of the width of the sub-groove rubber 19 in the direction perpendicular to the groove center line.

  In the configuration of FIG. 2, the profile of the inner cross belt 141 on the inner side in the tire radial direction (reference numeral omitted in the drawing) has a profile portion that protrudes toward the tire lumen along the lower groove profile portion Pri. ing. Furthermore, the profile of the carcass layer 13 has a profile portion that protrudes toward the tire lumen along the lower groove profile portion Pri. For this reason, in the groove region Ai of the outermost circumferential main groove 22, all the profiles of the carcass layer 13 and the pair of cross belts 141 and 142 are partially curved so as to protrude toward the tire lumen side. have. Such a configuration is preferable in that the dent of the outer cross belt 142 in the sub-groove region Ai can be appropriately formed while the distance between the cords of the carcass layer 13 and the pair of cross belts 141 and 142 is increased.

  However, the present invention is not limited to this, and in the sub-groove region Ai, only the profile Pr of the outer cross belt 142 has a partially curved shape so as to protrude toward the tire lumen, and the carcass layer 13 and the inner cross The profile of the belt 141 may have a shape that protrudes outward in the tire radial direction (not shown). Alternatively, the profile of the pair of cross belts 141 and 142 has a shape that is partially curved so as to be convex toward the tire lumen, and the profile of the carcass layer 13 has a shape that is convex outward in the tire radial direction. It may be done (not shown).

  In the configuration of FIG. 1, the lower groove profile portion Pri is formed only below the outermost circumferential main groove 22 on the outer side in the vehicle width direction, and below the outermost main groove 22 on the inner side in the vehicle width direction. Not formed. For this reason, the profile Pr of the outer cross belt 142 has a shape that protrudes outward in the tire radial direction over the entire inner region in the vehicle width direction with the tire equatorial plane CL as a boundary. In general, the groove crack is likely to occur in the outermost circumferential main groove 22 in the outer region in the vehicle width direction. For this reason, the lower groove profile portion Pri is formed below the outermost circumferential main groove 22 on the outer side in the vehicle width direction, whereby damage to the outer cross belt 142 caused by the groove crack can be appropriately suppressed.

  In the configuration in which the lower groove profile portion Pri is formed only under the outermost circumferential main groove 22 on the outer side in the vehicle width direction as described above, the pneumatic tire 1 is provided on the side having the lower groove profile portion Pri. It is preferable to have a mounting direction display unit (not shown) that designates mounting on the vehicle with the width direction outside. The mounting direction display part is configured by, for example, marks or irregularities attached to the sidewall part of the tire. For example, ECER30 (European Economic Commission Regulation Article 30) obligates the installation of a mounting direction display section on the side wall that is on the outer side in the vehicle width direction when the vehicle is mounted.

  However, the present invention is not limited to this, and the profile Pr of the outer cross belt 142 may include a groove lower profile portion Pri below the left and right outermost circumferential main grooves 22 and 22 (not shown).

  In addition, as shown in FIG. 2, the outermost circumferential main groove 22 is preferably located at a distance of 40% to 80% of the tire ground contact half width TW / 2 from the tire equatorial plane CL.

  The tire ground contact width TW is the contact surface between the tire and the flat plate when the tire is mounted on the specified rim to apply the specified internal pressure and is placed perpendicular to the flat plate in a stationary state and applied with a load corresponding to the specified load. It is measured as the maximum linear distance in the tire axial direction.

[Tire manufacturing method]
The general pneumatic tire 1 is manufactured by the following manufacturing process. First, each member such as a bead wire constituting the bead core 11, a carcass ply constituting the carcass layer 13, belt plies 141 to 143 constituting the belt layer 14, a tread rubber 15, a sidewall rubber 16, and a rim cushion rubber 17 is formed by a molding machine. To form a green tire (not shown). Next, this green tire is filled in a tire vulcanization mold (not shown). Next, the vulcanization mold is heated, the green tire is expanded radially outward by a pressurizing device, and comes into contact with a tire molding die (particularly, a tread surface molding portion) of the tire vulcanization mold. Next, when the green tire is heated, rubber molecules and sulfur molecules in the tread portion are bonded to each other and vulcanization is performed. At this time, the shape of the tire molding die is transferred to the tread surface of the green tire, and the tread pattern of the pneumatic tire 1 is molded. Thereafter, the vulcanized tire is pulled out from the tire vulcanization mold and taken out.

  In the above manufacturing process, the profile Pr of the outer cross belt 142 can be formed by the following process, for example. First, in the green tire molding step, a recess that forms the groove lower profile portion Pri is formed in advance at a position corresponding to the outermost circumferential main groove 22 of the outer cross belt 142. For example, after the cross belts 141 and 142 are disposed on the outer periphery of the carcass layer 13, a part of the outer cross belt 142 may be pressed from the outer peripheral surface side to be recessed, or the outer cross belt that is curved in advance and has a recess. 142 may be laminated on the carcass layer 13. Thereafter, the tread rubber 15 is disposed on the outer periphery of the outer cross belt 142, and a tire vulcanization molding process is performed. Then, at the time of vulcanization molding, the tread rubber 15 is filled in the recess of the outer cross belt 142 by the blade of the tire molding die pressing the tread rubber 15. As a result, the lower groove profile portion Pri of the outer cross belt 142 that protrudes toward the tire lumen side is formed in a sectional view in the tire meridian direction.

[effect]
As described above, the pneumatic tire 1 includes the carcass layer 13, the pair of cross belts 141 and 142 disposed on the outer periphery of the carcass layer 13, and the tread disposed on the outer periphery of the pair of cross belts 141 and 142. The rubber 15 includes a plurality of circumferential main grooves 21 and 22 extending in the tire circumferential direction, and a plurality of land portions 31 to 33 defined by the circumferential main grooves 21 and 22 (see FIG. 1). In addition, the profile Pr of the outer cross belt 142 has a shape that protrudes toward the tire lumen and is located in the groove region Ai of the outermost circumferential main groove 22 in a cross-sectional view in the tire meridian direction. Pri (in FIG. 2, a portion having a radius of curvature Ri) and a first profile portion (in FIG. 2) that has a shape that is convex outward in the tire radial direction and that is connected to the inner end in the tire width direction of the lower groove profile portion Pri. And a portion having a radius of curvature Ro1 (not shown in the figure), and a second profile portion having a shape protruding outward in the tire radial direction and connected to an outer end portion in the tire width direction of the lower groove profile portion Pri (see FIG. 2 includes a portion having a curvature radius Ro2 (not shown in the drawing) (see FIG. 2).

  In such a configuration, (1) since the profile Pr of the outer intersecting belt 142 is convex toward the tire lumen side is provided in the groove region Ai of the outermost circumferential main groove 22, the outermost circumferential main groove 22 is provided. The groove bottom gauge G1 from the groove bottom to the outer cross belt 142 increases. As a result, damage to the outer cross belt 142 due to the growth of groove cracks is suppressed, and there is an advantage that the belt durability performance of the tire is improved.

  Further, (2) since the profile Pr of the outer cross belt 142 is convex in the tire lumen side is partially provided in the groove region Ai of the outermost circumferential main groove 22, the circumferential direction of the entire tread The volume of the tread rubber 15 can be reduced as compared with a configuration (not shown) that increases the sub-groove gauge of the main groove. Thereby, there exists an advantage which can ensure appropriately the rolling resistance of a tire.

  (3) Since the profile Pr of the outer cross belt 142 protrudes outward in the tire radial direction, the first profile portion and the second profile portion are provided on the left and right of the lower groove profile portion Pri. The ground contact shape of the tread portion center region and the shoulder region is appropriately secured. Thereby, there exists an advantage by which the rolling resistance of a tire is ensured appropriately.

  Further, in this pneumatic tire 1, the outermost circumferential main groove 22 is at least one region with the tire equator plane CL as a boundary, and from the tire equator plane CL to 40 [%] or more of the tire ground contact half width TW / 2 to 80 [%] It is arranged at the following distance (see FIG. 2). In the outermost circumferential main groove 22 at such a position, groove cracks tend to occur. Accordingly, the groove bottom region Ai of the outermost circumferential main groove 22 is provided with the groove lower profile portion Pri in which the profile Pr of the outer cross belt 142 is convex toward the tire lumen side, so that the outer side caused by the growth of the groove cracks. There is an advantage that damage to the cross belt 142 is effectively suppressed.

  Moreover, in this pneumatic tire 1, the curvature radius Ri (see FIG. 2) of the lower groove profile portion Pri is in the range of 10 [mm] ≦ Ri ≦ 50 [mm]. Thereby, there exists an advantage by which the curvature radius Ri of the groove part profile Pri is optimized. That is, by satisfying 10 [mm] ≦ Ri, the radius of curvature Ri is ensured, the shape of the profile portion Pri below the groove is moderate, and the shape of the profile Pr of the outer cross belt 142 is appropriately secured. Further, since Ri ≦ 50 [mm], the radius of curvature Ri is set to be small, and the maximum protrusion amount D (see FIG. 3) of the lower groove profile portion Pri is secured. Thereby, the sub-groove gauge G1 of the outermost circumferential main groove 22 is ensured, and the function of the sub-groove profile portion Pri is appropriately secured.

  Moreover, in this pneumatic tire 1, the curvature radius Ro1 (refer FIG. 2) of the 1st profile part exists in the range of 150 [mm] <= Ro1 <= 2000 [mm]. Thereby, there exists an advantage by which the contact shape of the tread part center area | region which makes the outermost peripheral direction main groove 22 a boundary is optimized. That is, by satisfying 150 [mm] ≦ Ro1, the curvature radius Ro1 is ensured, and the situation where the ground contact shape is vertically long in the tire circumferential direction is suppressed. Moreover, since it is Ro1 <= 2000 [mm], it is suppressed that the curvature radius Ro1 becomes excessive, and the situation where the contact pressure of a tread part center area | region becomes lower than the contact pressure of a shoulder area | region is suppressed.

  In this pneumatic tire 1, the radius of curvature Ro2 (see FIG. 2) of the second profile portion is in the range of 50 [mm] ≦ Ro2 ≦ 800 [mm]. Thereby, there exists an advantage by which the contact shape of the tread part shoulder area | region which makes the outermost peripheral direction main groove 22 a boundary is optimized. That is, by satisfying 50 [mm] ≦ Ro2, the curvature radius Ro2 is ensured, and a situation where the ground contact width becomes narrower than the appropriate value of the size is suppressed. Further, by satisfying Ro2 ≦ 800 [mm], it is suppressed that the radius of curvature Ro2 is excessive, and a situation in which the contact pressure in the tread shoulder region is significantly higher than the contact pressure in the center region is suppressed. The

  Further, in the pneumatic tire 1, a virtual arc (broken line in FIG. 3) in contact with the first profile portion and the second profile portion, and the lower profile portion Pri side of the first profile portion and the second profile portion on the virtual arc. When defining the end points P1 and P2 (see FIG. 3), the distance Wb (Wb1 and Wb2 in FIG. 3) from the groove center line of the outermost circumferential main groove 22 to the end points P1 and P2, and the outermost circumferential main groove The groove width GW of 22 has a relationship of 0.40 ≦ Wb / GW ≦ 0.80. Thereby, there exists an advantage by which the width | variety of the profile part Pri below a groove | channel is optimized. That is, by satisfying 0.40 ≦ Wb / GW, the width of the lower groove profile portion Pri is appropriately secured, and the function of the lower groove profile portion Pri is ensured. Further, when Wb / GW ≦ 0.80, a situation in which the width of the sub-groove profile portion Pri is excessive is suppressed, and the regions of the first profile portion and the second profile portion are appropriately secured.

  Moreover, in this pneumatic tire 1, the end point P2 (see FIG. 3) on the outer side in the tire width direction is on the inner side in the tire width direction than the tire ground contact end T (see FIG. 2). Thereby, there exists an advantage by which the area | region of a 2nd profile part is ensured appropriately.

  Further, in the pneumatic tire 1, when defining a virtual arc (broken line in FIG. 3) in contact with the first profile portion and the second profile portion, the maximum protrusion amount D of the sub-groove profile portion Pri with the virtual arc as a reference. (See FIG. 3) is in the range of 0.6 [mm] ≦ D ≦ 3.3 [mm]. Thereby, there exists an advantage by which the maximum protrusion amount D of the profile part Pri below a groove | channel is optimized. That is, by satisfying 0.6 [mm] ≦ D, the sub-groove gauge G1 of the outermost circumferential main groove 22 is secured, and the effect of improving the belt durability performance is secured. Moreover, by being D <= 3.3 [mm], the situation where the sub-groove gauge G1 becomes excessive is suppressed, and deterioration of the rolling resistance of a tire is suppressed.

  Further, in this pneumatic tire 1, a sub-groove gauge G <b> 2 (not shown in the drawing) of the center circumferential main groove 21 and a sub-groove gauge G <b> 1 (see FIG. 3) of the outermost circumferential main groove 22 are 0. 6 [mm] ≦ G1-G2. Accordingly, there is an advantage that the sub-groove gauge G1 of the outermost circumferential main groove 22 is appropriately secured and the effect of improving the belt durability performance is secured.

  Further, in the pneumatic tire 1, when defining a virtual arc (broken line in FIG. 3) in contact with the first profile portion and the second profile portion, the maximum protrusion amount D of the sub-groove profile portion Pri with the virtual arc as a reference. And the sub-groove gauge G1 of the outermost circumferential main groove 22 have a relationship of 0.40 ≦ D / (G1-D) ≦ 1.70 (see FIG. 3). Thereby, there exists an advantage by which the maximum protrusion amount D of the profile part Pri below a groove | channel is optimized. That is, by satisfying 0.40 ≦ D / (G1-D), the sub-groove gauge G1 is appropriately increased by the maximum protrusion amount D, and the effect of improving the belt durability performance is appropriately ensured. Further, since D / (G1-D) ≦ 1.70, the situation where the maximum protrusion amount D is excessive is suppressed, and the shape of the profile Pr of the outer cross belt 142 is optimized.

  Moreover, in this pneumatic tire 1, the tread rubber 15 includes a cap tread 151 that forms a tread surface, and an under tread 152 that is disposed below the cap tread 151 (see FIG. 1). In addition, the pneumatic tire 1 has physical properties superior in heat resistance to the undertread 152, and also includes virtual arcs (broken lines in FIG. 5) in contact with the first profile portion and the second profile portion and the outer periphery of the outer cross belt 142. An under-groove rubber 19 is provided in a region surrounded by the surface (see FIG. 5). In such a configuration, the grooved rubber 19 suppresses heat generation in the grooved region Ai of the outermost circumferential main groove 22 during rolling of the tire, so that the growth of groove cracks due to the deterioration of the rubber in the grooved region Ai occurs. It is suppressed. Thereby, there exists an advantage by which the damage of the outer side cross belt 142 by a groove crack is suppressed. In particular, since the under-groove rubber 19 is disposed so as to fill the recess of the under-groove profile portion Pri of the outer cross belt 142, there is an advantage that belt breakage during turning at a large steering angle can be suppressed.

  Further, in this pneumatic tire 1, the profile of the cross belt 141 on the inner side in the tire radial direction (reference numeral omitted in the drawing) has a profile portion that is convex toward the tire lumen along the lower groove profile portion Pri ( (See FIG. 3). In such a configuration, there is an advantage that the recess of the outer cross belt 142 in the sub-groove region Ai can be appropriately formed while the distance between the cords of the pair of cross belts 141 and 142 is increased.

  Moreover, in this pneumatic tire 1, the profile of the carcass layer 13 (not shown in the figure) has a profile portion that protrudes toward the tire lumen along the lower groove profile portion Pri (see FIG. 3). In such a configuration, there is an advantage that the recess of the outer cross belt 142 in the sub-groove region Ai can be appropriately formed while the distance between the cords of the carcass layer 13 and the pair of cross belts 141 and 142 is increased.

  The pneumatic tire 1 also includes a mounting direction display unit that designates mounting on the vehicle with the side having the lower groove profile portion Pri on the outside in the vehicle width direction (see FIG. 1). In such a configuration, the lower groove profile portion Pri is formed in the lower groove region Ai of the outermost circumferential main groove 22 on the outer side in the vehicle width direction where groove cracks are likely to occur. Thereby, there is an advantage that the effect of improving the belt durability by the under-groove profile portion Pri can be effectively obtained.

  In addition, the method for manufacturing the pneumatic tire 1 includes a step of forming a recess that forms the groove lower profile portion Pri at a position corresponding to the outermost circumferential main groove 22 of the outer cross belt 142 in a green tire molding process. And vulcanizing the green tire. In such a configuration, a recess that forms the lower groove profile portion Pri is formed in the outer cross belt 142 in advance before the tire vulcanization molding step. Thereby, there exists an advantage which can form easily the under-groove profile part Pri which becomes a convex in the tire cavity part side.

  FIG. 6 is a chart showing the results of the performance test of the pneumatic tire according to the embodiment of the present invention.

  In this performance test, (1) belt durability performance and (2) rolling resistance were evaluated for a plurality of types of test tires. Further, a test tire having a tire size of 195 / 65R15 91S is assembled to a rim having a rim size of 15 × 6 J, and an air pressure of 230 [kPa] and a maximum load specified by JATMA are applied to the test tire. In addition, the test tire is attached to all wheels of a front wheel drive vehicle having a displacement of 1.6 [L], which is a test vehicle.

  (1) The belt durability performance is evaluated by a low-pressure durability test using an indoor drum tester. Then, the travel speed is increased by 1 [km / h] every 12 hours from the initial speed of 5 [km / h], and the travel time until the tire breaks down is measured. Then, based on this measurement result, index evaluation using the conventional example as a reference (100) is performed. This evaluation is preferable as the numerical value increases.

  (2) In the evaluation relating to the rolling resistance, an indoor drum tester is used, and the resistance force at a speed of 50 km / h is measured and evaluated. This evaluation is performed by index evaluation using the conventional example as a reference (100), and the larger the value, the better. Moreover, if a numerical value is 95 or more, it can be said that deterioration of rolling resistance is suppressed appropriately.

  The test tires of Examples 1 to 7 have the configurations of FIGS. 1 to 4, and the profile Pr of the outer cross belt 142 is in the groove inner region Ai of the outermost circumferential main groove 22 on the outer side in the vehicle width direction. A groove lower profile portion Pri that is convex on the portion side is provided. Further, the outermost circumferential main groove 22 is at a position of 70 [%] of the tire ground contact half width TW / 2, and the groove width GW of the outermost circumferential main groove 22 is GW = 10 [mm]. Further, the radii of curvature Ro1 and Ro2 of the first profile portion and the second profile portion of the outer cross belt 142 are Ro1 = 500 [mm] and Ro2 = 600 [mm]. Further, the test tire of Example 8 has the configuration of FIG. 5, and includes a grooved rubber 19 in the grooved region Ai of the outermost circumferential main groove 22. The tan δ value of the undertread 152 is 0.10, and the tan δ value of the under-groove rubber 19 is 0.05.

  The test tires of the conventional examples 1 and 2 have the configuration in which the profile Pr of the outer cross belt 142 is not provided with the lower groove profile portion Pri in the configuration of the first embodiment, and the shape is convex outward in the tire radial direction over the entire region. I have. Further, the radius of curvature of the profile Pr of the outer cross belt 142 is 600 [mm] in the tread portion center region and 800 [mm] in the tread portion shoulder region.

  As shown in the test results, it can be seen that in the test tires of Examples 1 to 8, the belt durability performance is improved while maintaining the rolling resistance of the tire.

  1: pneumatic tire, 11: bead core, 12: bead filler, 13: carcass layer, 131, 132: carcass ply, 14: belt layer, 141: inner cross belt, 142: outer cross belt, 1421: belt cord, 1422 : Coat rubber, 143: Belt edge cover, 15: Tread rubber, 151: Cap tread, 152: Under tread, 16: Side wall rubber, 17: Rim cushion rubber, 18: Inner liner, 19: Rubber under groove, 21, 22 : Circumferential main groove, 31-33: Land

Claims (15)

A carcass layer, a pair of intersecting belts disposed on an outer periphery of the carcass layer, a tread rubber disposed on an outer periphery of the pair of intersecting belts, a plurality of circumferential main grooves extending in a tire circumferential direction, A pneumatic tire comprising a plurality of land portions divided into circumferential main grooves,
When defining the intersecting belt on the outer side in the tire radial direction as an outer intersecting belt, and defining the circumferential main groove on the outermost side in the tire width direction as the outermost circumferential direction main groove,
The profile of the outer cross belt has a shape that is convex toward the tire lumen side in a cross-sectional view in the tire meridian direction, and the lower groove profile portion located in the lower groove region of the outermost circumferential main groove, and the tire diameter A first profile portion having a convex shape outward in the direction and connected to an inner end portion in the tire width direction of the lower groove profile portion; and a tire having a convex shape outward in the tire radial direction and the lower groove profile portion A pneumatic tire comprising: a second profile portion connected to an outer end portion in the width direction.   The outermost circumferential main groove is arranged in at least one region with the tire equator plane as a boundary and at a distance of 40% to 80% of the tire ground contact half width from the tire equator plane. The described pneumatic tire.   The pneumatic tire according to claim 1 or 2, wherein a curvature radius Ri of the under-groove profile portion is in a range of 10 [mm] ≤ Ri ≤ 50 [mm].   The pneumatic tire according to any one of claims 1 to 3, wherein a curvature radius Ro1 of the first profile portion is in a range of 150 [mm] ≤ Ro1 ≤ 2000 [mm].   The pneumatic tire according to any one of claims 1 to 4, wherein a curvature radius Ro2 of the second profile portion is in a range of 50 [mm] ≤ Ro2 ≤ 800 [mm]. A virtual arc in contact with the first profile portion and the second profile portion, and end points P1, P2 on the side of the groove profile portion of the first profile portion and the second profile portion on the virtual arc,
A distance Wb from a groove center line of the outermost circumferential main groove to the end points P1 and P2 and a groove width GW of the outermost circumferential main groove have a relationship of 0.40 ≦ Wb / GW ≦ 0.80. The pneumatic tire according to any one of Items 1 to 5.   The pneumatic tire according to claim 6, wherein an end point P2 on the outer side in the tire width direction is on the inner side in the tire width direction with respect to the tire ground contact end T. Defining a virtual arc in contact with the first profile part and the second profile part;
The maximum protrusion amount D of the under-groove profile portion with respect to the virtual arc is in a range of 0.6 [mm] ≦ D ≦ 3.3 [mm]. Pneumatic tires. Defining the second circumferential main groove on the tire equatorial plane side adjacent to the outermost circumferential main groove as a center circumferential main groove;
The sub-groove gauge G2 of the center circumferential main groove and the sub-groove gauge G1 of the outermost circumferential main groove have a relationship of 0.6 [mm] ≦ G1-G2. Pneumatic tire described in one. Defining a virtual arc in contact with the first profile part and the second profile part;
The relationship of 0.40 ≦ D / (G1-D) ≦ 1.70 between the maximum protrusion amount D of the lower groove profile portion with respect to the virtual arc and the lower groove gauge G1 of the outermost circumferential main groove. The pneumatic tire according to any one of claims 1 to 9. The tread rubber comprises a cap tread that forms a tread surface; and an under tread disposed in a lower layer of the cap tread; and
Grooves having physical properties superior in heat resistance than the undertread, and disposed in a region surrounded by a virtual arc in contact with the first profile portion and the second profile portion and an outer peripheral surface of the outer cross belt The pneumatic tire according to claim 1, further comprising a lower rubber.   The pneumatic tire according to any one of claims 1 to 11, wherein a profile of the cross belt on the inner side in the tire radial direction has a profile portion that is convex toward the tire lumen along the under-groove profile portion.   The pneumatic tire according to any one of claims 1 to 12, wherein the profile of the carcass layer has a profile portion that protrudes toward the tire lumen along the profile region below the groove.   The pneumatic tire according to any one of claims 1 to 13, further comprising a mounting direction display unit that designates mounting on a vehicle with a side having the under-groove profile portion positioned outside in the vehicle width direction. It is a manufacturing method of the pneumatic tire according to any one of claims 1 to 14,
In the green tire forming step, a step of forming a dent constituting the groove lower profile portion at a position corresponding to the outermost circumferential main groove of the outer cross belt;
And a step of vulcanizing and forming the green tire.

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